This invention relates generally to an artificial tooth root and particularly to an artificial tooth root that has improved impact resistance.
Recently, there has been much research into dealing with natural teeth damaged through disease or accident by extracting the tooth and implanting an artificial root which has the same function as the original natural tooth.
FIGS. 1 and 2 show a prior art commercialized sapphire artificial tooth root implantation. In FIG. 1, after the damaged tooth (not shown) has been extracted as shown by the arrow, recess 4 is formed in alveolar bone portion 2 and sapphire tooth root 6 is implanted. In FIGS. 1 and 2 reference numeral 8 denotes the alveolar bone and 10 denotes the alveolar ridge or gingiva.
A metal material that is compatible with live tissue is used for artificial tooth root 6. This kind of tooth root has excellent mechanical strength but its biological bondability with live tissue is not satisfactory and, consequently, special means for fastening the tooth root are required. Metal is also not desirable in that, depending on the type of metal used, metal ions harmful to live tissue may diffuse out of the tooth root.
In recent years ceramics such as single crystal alumina have been developed for artificial tooth roots and put into practical use. These ceramic tooth roots have an advantage over metal in that there is no diffusion to harmful material into the tissue but they also provide poor bondability. Material that does provide excellent biological bonding with live tissue is ceramics such as biologically activated glass, TCP (tricalcium phosphate) or apatite. These materials, however, while having excellent biological bondability, have insufficient mechanical strength.
In the prior art it has been impossible to obtain an artificial tooth root that has both good biological bonding and good mechanical strength. There have, accordingly, been problems with impact resistance when brittle food is chewed. With a tooth root that has only mechanical strength, for example, the pressure generated from chewing is transmitted to alveolar bone 8 and the surrounding area which may be damaged by this pressure, and when used for a long period of time, may result in tooth root 6 coming loose from alveolar bone portion 2. Where the biological bonding characteristics are excellent, on the other hand, damage to the tooth root itself becomes a problem.